Effect of Gasoline Fuel Additives on Combustion and Engine Performance

7.3
 
Further Work 
Although the current study has covered an extensive selection of additives and 
experimental methods, a number of improvements to the analysis could be 
implemented to advance the understanding of the effects of additives on fundamental 
combustion processes.
Among the main enhancements to the spray investigations would be to study 
atomisation in higher back pressure and temperature conditions. Such environment 
possesses greater likeness to engine working conditions, especially that of late 
injection timing under stratified injection strategy. Since current investigations have 
shown no significant effect on fuel atomisation to result from additive usage in 

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7.3 Further Work 
168 
ambient conditions, the higher energy environment would highlight the additive effect 
on evaporation characteristics. The only limitation of higher evaporation rates is the 
increased beam steering effect with a laser diffraction system, though, as in current 
work, the effect can be taken into account with appropriately selected settings on the 
equipment. 
Present investigations on the effects of additives on combustion characteristics 
only included compounds that are intended to modify combustion reactions. Although 
work on fuel atomisation suggested that additives have no unwanted effects on the 
physical properties of the base fuel, carrying out combustion investigations with a 
range of additives from all functional groups would facilitate similar judgment on their 
effects on combustion characteristics. Additionally lower concentrations of CI-A 
additive than the currently employed 1X could be investigated with regards to its effect 
on CO emissions and KI. 
A final suggestion for future experiments on fuel additives would be to 
undertake engine testing with a direct injection fuel metering system. Although 
carburettor equipped engine testing permits investigation into combustion 
characteristics of fuels well and the lack of electronic fuel metering systems results in 
low hardware variability, with ever stringent emissions and fuel consumption 
regulations, an understanding of the fuel additive effects in engines equipped with 
state-of-the-art technology is paramount. While it is evident that DI fuel metering 
systems can suffer from large shot-to-shot variability, DI engine testing with additives 
would demonstrate their effect in real life conditions on combustion and emissions 
characteristics. Moreover, DI engine testing would tie together spray and combustion 
analysis from current study whereby, with the addition of particulate matter and 
unburnt hydrocarbon content in the emissions, the correlation between atomisation 
quality and combustion performance and their dependence on fuel additives could be 
evaluated.